Further to his 2007 investigations into the effects of cannabis on schizophrenia risk, Dr Tim Karl has teamed up with Dr Jonathan Arnold and Prof. Iain McGregor at the University of Sydney, and Prof. Xu Feng Huang at the University of Wollongong to devise a broader study. The team’s proposal has been awarded a National Health and Medical Research Council (NHMRC) Project Grant of $437,125. In the highly competitive environment of NHMRC funding, this is a major win for schizophrenia research.

Dr Tim Karl – with some of the most valuable mice in the world.

The new study will seek to answer the question of why some adolescent cannabis users develop schizophrenia while others do not. Does the risk depend upon a genetic vulnerability?

In the earlier study, Dr Karl used genetically modified ‘knockout’ mice in which the NRG1 gene expression had been reduced. When dosed with THC (the psychotropic agent in cannabis), these mice were shown to be more sensitive to its behavioural effects compared to unaltered ‘wildtype’ mice. However, as the earlier study used a one-off dose of THC, and susceptibility to schizophrenia is associated with long-term cannabis usage, a further study was indicated in which repeated doses of THC and annabidiol (another component of cannabis) would be applied to dolescent as well as to mature mice. The new study will accomplish this, and also measure how such dosage affects schizophrenia-rlated receptors (e.g. cannabinoid, glutamate, dopamine) in the brains of both the knockout’ and ‘wild-type’ mice.

The results of this study will provide an extensively characterised animal model of how genetic vulnerability to schizophrenia interacts with the effects of cannabis, thereby helping to clarify the complex relationship between the drug and schizophrenia.

Dr Karl was also awarded the inaugural SRI ‘Early Career Researcher Award’ of $10,000 to help fund his work.

A study conducted at the Schizophrenia Research Institute centre at the University of Newcastle has shown that specific mRNA expression levels in the brain’s superior temporal gyrus (STG) are altered in schizophrenia. As the STG encompasses the primary auditory cortex, and the genes are involved in regulating neurotransmission and neurodevelopment, these alterations may play an integral role in the development and symptoms of schizophrenia.

Using post-mortem tissue from schizophrenia-affected brains and matched controls, this microarray study examined 19,000 genes in the STG, finding that 191 expressed at higher levels and 428 were expressed at lower levels in schizophrenia compared to controls. This overall ‘down-regulation’ of gene expression in schizophrenia may contribute to the cognitive deficiencies and symptoms of the illness.

With the help of volunteers recruited from the Institute’s Schizophrenia Research Register, researchers from the University of NSW led a collaborative study, which aimed to define whether the negative symptom of ‘blunted affect’ in schizophrenia (characterised by reduced emotion expressivity alongside normal emotion experience) was due to deliberate self-suppression of emotional responses.

41 people with schizophrenia and 38 healthy controls completed the ‘Emotion Regulation’ questionnaire in addition to measures of. mood, symptom severity, cognitive and social functioning.The results indicated that although in both groups reported use of specific strategies related systematically to mood and social functioning, there was no difference between schizophrenia participants and controls regarding their habitual use of different emotion regulation strategies.

These results suggest that the common symptom of ‘blunted affect’ is due to more fundamental deficits than overuse of self-suppression: a finding which may help to refine cognitive behavioural therapy techniques aimed at remediation of social difficulties in schizophrenia.

Research discoveries over recent decades have defined many differences between people with schizophrenia and those without: structural, functional and genetic differences in the brain, as well ascognitive/perceptual differences.

Professors Ulli Schall and Pat Michie of the University of Newcastle are leading a collaborative group of the SRI Cognition and Connectivity Panel to apply the knowledge from these discoveries in a multi-centre study aiming to define the factors involved in schizophrenia onset.

The study will recruit young people (12-25 years) from clinical centres in Newcastle, Orange and Sydney. Of the many young people presenting at these centres each year, up to 130 are deemed to be at ultra-high risk (UHR) of developing a psychotic disorder such as schizophrenia. Records show that 30-50 percent of such patients develop psychosis within 12 months.

Each UHR individual will be age/sex matched with a healthy control, and both will receive a sequence of tests devised from recent discoveries. These include MRI brain scans to measure cortical differences; DNA profiling to detect changes in gene expression; mismatch negativity tests to detect auditory cognitive abnormalities – as well as a number of cognitive/perceptual tests.

The 5-year study aims to compare results from the UHR participants who develop schizophrenia with those that do not, and with matched controls, to closely map the transition from high risk to psychosis. The study has received funding from the Hunter Medical Research Institute, and the University of Newcastle Priority Centre for Brain and Mental Health Research & Research Grants Committee.

Many studies have now confirmed that abnormalities in the Neuregulin-1 (NRG1) gene are found in people with schizophrenia, and researchers are looking closely at this gene as both a possible ‘marker’ of schizophrenia risk and a source of new treatment. The Institute’s Developmental Neurobiology Panel has combined forces to further define the links between NRG1, brain development and schizophrenia.

NRG1 is one of the largest genes in the human genome, sprawling over some 1,125,000 units of DNA, and it is expressed widely throughout the brain. What attracts the attention of so many schizophrenia researchers is that NRG1 seems to regulate key neurodevelopmental processes in the brain during puberty, a time which is particularly relevant to the development and onset of schizophrenia.

Members of the Institute’s Developmental Neurobiology Panel are initiating a large scale collaborative project in which six SRI schizophrenia research centres will use their on-site expertise and research techniques to examine a specific component of NRG1’s role in brain development and schizophrenia. To support this research two research resources are being developed: post mortem human brain tissue from a large number of individuals with schizophrenia and matched controls, and brain tissue from mice with reduced levels of Neuregulin-1. Once obtained, this tissue will be distributed to the various centres, for multifaceted investigations, which will encompass a formidable range of research techniques and expertise including:

1. Dr Katerina Zavitsanou’s group at the Australian Nuclear Science and Technology Organisation will investigate NRG1-related protein expression in the human brain.

2. At the Garvan Institute, Dr Tim Karl’s team will investigate how NRG1 depletion and exposure to cannabis influences behaviour (see below).

3. Prof. Cyndi Shannon Weickert’s team at the Schizophrenia Research Laboratory aim to determine how the reduction of NRG1 expression in mice affects their viability as models for schizophrenia.

4. Dr Jan Fullerton and Dr John Kwok at the Prince of Wales Medical Research Institute will map specific variants in the NRG1 gene that are associated with schizophrenia.

5. Dr Murray Cairns and Dr Paul Tooney at the University of Newcastle plan to investigate the role of microRNA in modulating NRG1 gene expression in the human brain tissue.

6. Prof. Xu-Feng Huang’s team at the University of Wollongong will use human tissue and ‘knockout’ mice to investigate the relationship between NRG1 and a range of receptors.

This multi-centre research approach will provide a comprehensive understanding and characterisation of NRG1, how it affects brain development and its role in schizophrenia from multiple perspectives. It will also develop the infrastructure necessary for the Developmental Neurobiology Panel to investigate other potential ‘markers’ for the illness in the future.

A collaborative MRI brain imaging study (1) initiated by Dr Nadia Solowij’s group at the University of Wollongong set out to determine whether heavy cannabis use by people with no mental disorders was associated with anatomical changes in the hippocampus and the amygdala – two brain areas known to be altered in schizophrenia.

The cannabis users were found to have an averaged 12 per cent volume reduction of the hippocampus, and a 7 per cent reduction of the amygdala compared to controls.

MRI brain scans showing a 12% reduction of the hippocampus in a long-term cannabis user.

Dr Solowij commented, “These results demonstrate a link between long-term cannabis users and psychotic experiences, such as persecutory beliefs and social withdrawal. Long-term users have also progressed the loss of memory by around 15 years. With an average age of 39, the trial group had the memory capabilities of a 55 year-old. This loss of memory could be likened to the damage suffered by patients with mild traumatic brain injury.”

With further support from the Schizophrenia Research Institute, Dr Solowij’s group is extending this research into schizophrenia populations who do and do not use cannabis.

Cannabis and Psychosis Risk

Cannabis use leads to an increase in risk of psychosis and many psychotic episodes could be avoided, according to a recent review of studies. Dr Martin Cohen has led a group of Schizophrenia Research Institute researchers located at the Universities of Newcastle and Wollongong who have completed a major review (2) of 145 studies linking cannabis use to schizophrenia.

The review came to three important conclusions:

The risk of psychosis is increased by around 40 per cent in people who have used cannabis;

There is a dose-response effect, leading to an increased risk of 5-200 per cent in the most frequent users;

If using cannabis increases risk, as research suggests, 14 per cent of psychotic outcomes in young people would not have occurred if cannabis had not been consumed.

Other research has found that cannabis use prior to the age of 15 confers the greatest risk, due to the drug’s effect upon the neurodevelopmental processes occurring in the adolescent brain.

Many other studies have contributed to the literature on the subject, warranting the comprehensive review of all data to assist clinicians in evaluating cannabis use in patients.

When she was a teenager, Cyndi Shannon Weickert’s twin brother showed the first signs of schizophrenia.

“It was very frightening to observe,” she recalls. No doubt. Yet like the budding young scientist she was, Shannon Weickert watched carefully as her brother’s devastating mental illness progressed.

She saw first-hand many of the distressing symptoms of schizophrenia, from delusions and hallucinations to depression, social withdrawal and a loss of motivation, drive and initiative. Today, she is a neurobiologist, dedicated to unravelling the complex causes of his disease. “I saw it unfold and that helped me understand it,” she says.

Little wonder then that Shannon Weickert now heads a schizophrenia research project, jointly initiated by the Prince of Wales Medical Research Institute, the University of NSW and the Schizophrenia Research Institute. The SRI is a “virtual” collaboration of Australian biomedical researchers.

The ambition is to untangle many of the baffling genetic and biochemical threads driving the developmental brain disorder. While there are many scientific tacks to take, Shannon Weickert’s search is shaped by her expertise in brain development.

“I think of mechanisms that change with adolescence,” she explains. What changes? Hormones, of course, such as the so-called female hormone estrogen. That “of course” moment led Shannon Weickert and colleagues to look for genes implicated in estrogen’s business in the brain.

They hit paydirt. They discovered that mutations in a gene called the estrogen receptor alpha gene (ESR1) are linked to schizophrenia (Human Molecular Genetics 2008 17(15):2293-2309).

Now her group is looking for 80 volunteers, men and women, with schizophrenia willing to trial a drug used to regulate estrogen in the brain, along with their own medication. The trial drug was designed to treat osteoporosis and cancer, but Shannon Weickert suspects it will help modify the “negative” symptoms of schizophrenia — the antisocial, loss of get-up-and-go emotional states.

“We hope people will be more comfortable socially, be a little better motivated and have their thinking become clearer,” she explains.

Shannon Wieckert’s research illustrates how various branches of science are converging on causes of and cures for schizophrenia. This week, for instance, the journal Nature published reports from three enormous international consortia — two with Australian participants — that had scanned the genes of people with and without the illness, looking for more clues to its genetic underpinning.

As evolutionary biologist Simon Easteal notes, there are no immediate clinical implications of the findings. “But these papers appear to provide some evidence for possible clinical subtypes of schizophrenia and the lack of clear demarcation from (the intense mood swings of) bipolar disorder,” concludes Easteal, deputy director of the John Curtin School of Medical Research at Canberra’s Australian National University.

In other words, the ability to trawl through vast swathes of the human genome has allowed researchers to confirm that there’s no single gene driving schizophrenia. Instead, it’s a jumble of genetic glitches that ultimately come together to produce the terrible symptoms. Just how, why and where those glitches merge remains the unsolved mystery.

Enter scientists such as molecular biologist Murray Cairns, with Newcastle University in NSW and the SRI. He’s exploring the role tiny snippets of genetic material called micro ribonucleic acids (miRNAs) play in turning genes on or off. Because miRNAs themselves are influenced by non-genetic pressures, from diet to stress, they are a link between nature and nurture. They must be central to those troublesome paths to schizophrenia.

“I thought it could have something to do with how the genes (for schizophrenia) are regulated, rather than a series of genetic mutations,” he says of his recent discovery that miRNAs do indeed “disregulate” gene activity in the brains of people with schizophrenia. It’s a finding Cairns claims points to new “targets” for drug development.

University of Melbourne psychiatrist Michael Berk agrees that genetic work promises to help reveal which biochemical events are “upstream” and “downstream” in the biochemical pathway to schizophrenia.

Meanwhile, Berk — also with Barwon Health, The Geelong Clinic and the Orygen Research Centre — is exploring trails to near-term treatments. One exploits fundamental research about the damage so-called free radicals cause to body cells and DNA. Along with US and Swiss colleagues, Berk tried out the idea that battling free radicals by boosting levels of a powerful antioxidant
called glutathione might, like estrogen, reduce the “negative” symptoms of schizophrenia.

It does. A trial, with 83 people, reported last May in the journal Biological Psychiatry, showed that that a dietary supplement — N-acetyl cysteine (NAC) — taken by muscle-bound bodybuilders and partygoers to cure a hangover did, indeed, boost glutathione and reduce symptoms. “We know we’re on to something,” says Berk, who is beginning trials of NAC with people with bipolar disorder.

And proving that Shannon Weickert doesn’t have a monopoly on a good idea, Berk’s also involved in a three-centre trial in Victoria that uses estrogen to treat men and women. Instead of inspiration from developmental biology, though, this work’s based on insights for epidemiological, clinical and animal studies.

“The evidence is very clear that estrogen in the brain has a very powerful antipsychotic effect,” says team leader Jayashri Kulkarni, a psychiatrist with Monash University and The Alfred Psychiatry Research Centre.

Along with Victorian colleagues, Kulkarni reported seven years ago that estrogen helped female patients (Schizophrenia Research 2001;48:137-144). New confirmatory results will be published soon
in the Archives of General Psychiatry.

“It has a direct impact on dopamine and serotonin systems,” she says, pointing to two well-known paths to the hallucinations and delusions of schizophrenia — disruption of those neurotransmitters
in the brain.

In fact, those pathways work alongside one involving another neurotransmitter, acetylcholine, which is the target of chlorpromazine. Developed in 1950, it was the first drug developed for schizophrenia. As clinicians such as Berk and Kulkarni note, chlorpromazine and daughter drugs manage the psychotic symptoms of schizophrenia, hence the push for ways to help with negative
symptoms.

The study of tiny snippets of genetic material called micro RNAs is one of the hottest areas of medical research

Dr Murray Cairns.

Murray Cairns never planned to be a schizophrenia researcher. But when the little bio-tech firm for which he worked three years ago collapsed, the molecular biologist was open to all options.

“I was looking around and saw an advertisement for the Schizophrenia Research Institute,” he recalls from his office at the University of Newcastle in NSW. “They thought I had useful experience as a molecular biologist, but they didn’t have any idea that I’d come up with this branch of research,” he laughs.

It’s hardly surprising that the SRI — a “virtual” collaboration of Australian biomedical researchers with headquarters at the Garvan Institute in Sydney — had no inkling of what Cairns would get up to down in the lab. After all, nobody in Australia was doing anything like it. What’s more, the genetic tools of Cairns’ trade, so-called micro ribonucleic acids (miRNAs), were only discovered in people in 2000.

Now, Cairns has just published remarkable findings about the inner workings of schizophrenia. And miRNAs, tiny bits of genetic material, are hotter than hot in laboratories around the world. Like Cairns, researchers are excited about the power of the genetic snippets to help them understand the mechanisms of diseases, from schizophrenia to cancer, and to assist in the development of a brand new class of diagnostic tools and therapies for them.

Realistically, the potential of the emerging field of miRNA genetics is huge, claims molecular biologist and geneticist Greg Arndt: “It’s enormous. There’s an absolutely enormous potential.”

Arndt works for the Sydney research arm of the pharmaceutical giant Johnson and Johnson, and “Big Pharma” is not known for throwing money around frivolously. The fact that Arndt and his J&J colleagues overseas are exploring the role of miRNAs in colorectal cancer is telling.

“Colorectal cancer is one of the most prominent forms of cancer in the world,” Arndt says. “One thing that would be very useful for colorectal cancer would be new techniques for detecting the stages of the development of the disease. So we undertook to look at miRNAs at various stages in patient tissue. We saw there was altered activity in the miRNAs,” he explains.

Cairns and Arndt’s work reflects the realisation that miRNAs are very busy entities. That’s despite the fact that they’re small — only 20-22 bits, or “bases’, long — and make nothing. Larger RNA molecules produce “can-do” molecules such as proteins or enzymes. What miRNAs do is regulate the activity, or “expression”, of thousands of genes throughout the body.

Arndt’s findings about colorectal cancer are a perfect example. There, the miRNAs promote or suppress the development and spread of cancer cells.

Cairns notes another intriguing fact about miRNAs: “They’re promiscuous.” One miRNA can affect the expression of many different genes, and can mix-and-match with other miRNAs to regulate more genes which together are involved in a host of biochemical pathways in the body. Some of those pathways are known to play important roles in human development, stress responses and viral infections.

That’s why, like Arndt, molecular biologist Greg Goodall, with the Institute of Medical and Veterinary Science and the University of Adelaide sees “tremendous scope” for using miRNAs to unravel and control pathways that drive diseases. “This is such a new unexplored area that offers so many opportunities for experiencing the joy of discovery,” says Goodall.

Currently, he’s focusing on breast cancer. Goodall remains mum, but the word from observers such as Geoff Lindeman, a breast cancer expert at the Walter and Eliza Hall Institute in Melbourne, is that Goodall’s group has publications in the pipeline that will add to an important discovery revealed last month in the journal Nature.

As reported in The Australian (14/1), US researchers identified three miRNAs that halt the spread of breast cancer to the lungs and bones of women with the most dangerous forms of the disease. The team leader Joan Massague, head of the cancer biology and genetics program at the Memorial Sloan-Kettering Cancer Center in New York, said: “The tiny RNAs prevent the spread of cancer by interfering with the expression of genes that give cancer cells the ability to proliferate and migrate (to other parts of the body)”.

According to Massague, that makes miRNAs “tiny targets” for drug development: control the miRNAs and control the disease. Arndt agrees, pointing to two approaches. The first would be to give a patient a drug containing miRNAS to boost levels of critical miRNAS. That follows the findings from Massague’s team. When the three miRNAs they identified were low or absent, the cancer spread. But when they put them into cancer cells implanted in mice, the deadly cells could not spread.

Arndt says the second strategy is to directly target the miRNAs in a person’s body. Like more conventional therapies, drugs would boost or suppress miRNAs which themselves boost or suppress the activity of genes involved in a disease or condition.

But as Arndt’s work with colorectal cancer suggests, miRNAs also hold huge promise as diagnostic tools, helping doctors to detect diseases early on and to monitor the effectiveness of treatment. Astonishingly, while the entire field of human miRNA only got rolling in 2000, the Israeli firm Rosettta Genomics predicts it will have miRNA-based diagnostic and predictive tests for brain cancers on the market by the end of the year. Treatments for cancers and viruses are bound to follow in the next few years.

All this from a left-field discovery of an RNA “gene” in a nematode worm, first reported in the journal Cell in 1993. At the time conventional wisdom was that genes were found in deoxyribonucleic acid, the famous double-helix of DNA. Genes told single-stranded RNA what to do and the RNA got onto it, synthesising proteins. But to universal surprise that’s what the weird RNA worm “gene” appeared to do.

Further investigation uncovered the truth. The “gene” was a miRNA, says Goodall: “It was an unsuspected type of genetic regulator that is really just a small piece of RNA.” In other words, a totally new system of controlling what goes on in the human body had been discovered in a worm. The race is on to find out what regulates the newfound regulators.

That’s why Murray Cairns suspected that miRNAs had a role in the onset of the disordered thinking and hallucinations that are the hallmark of schizophrenia. “I thought it could have something to do with how the genes are regulated, rather than a series of genetic mutations,” he recalls.

To find out Cairns looked at a “thinking” brain region, the temporal cortex. He discovered that two-thirds of genes were more active, and one-third less active, in people who died from schizophrenia compared to people without the disorder. Significantly, the Cairns and SRI colleagues have just showed the differences correspond to levels of miRNAs in the brain, and have strong evidence that the miRNAs “disregulate” gene activity in the brains of people with schizophrenia.

Given the complexity of schizophrenia, it’s early days yet. But Cairns has big plans for the tiny regulators.